﻿794 
  Pit 
  O 
  CEEDING 
  S 
  OF 
  THE 
  NA 
  TIONAL 
  M 
  USE 
  UM. 
  vol. 
  xx. 
  

  

  internal 
  posteriorly. 
  Just 
  beneath 
  the 
  beak 
  is 
  an 
  elongated 
  tooth-like 
  

   thickening 
  of 
  the 
  inner 
  margin 
  which 
  consequently 
  curv^es 
  downward, 
  

   at 
  this 
  i)oint. 
  Muscular 
  scars 
  whitish, 
  inconsi)icuous. 
  The 
  external 
  

   surface, 
  so 
  far 
  as 
  visible, 
  seems 
  to 
  be 
  smoothish 
  with 
  irregular 
  lines 
  of 
  

   growth. 
  

  

  Length, 
  1.0 
  mm.; 
  height, 
  1.4 
  mm. 
  

  

  Two 
  valves, 
  station 
  049, 
  N. 
  lat. 
  40° 
  ;V, 
  W. 
  long. 
  70° 
  31', 
  in 
  100 
  fathoms, 
  

   1881. 
  This 
  species 
  is 
  encrusted 
  very 
  much 
  as 
  Cri/ptodon 
  {A.vinulus) 
  

   ferruflinosus, 
  but 
  is 
  quite 
  different 
  in 
  its 
  much 
  more 
  strongly 
  developed 
  

   hinge 
  and 
  ovate 
  form. 
  

  

  From 
  station 
  2113, 
  :^. 
  lat. 
  35° 
  20' 
  30", 
  W. 
  long. 
  75° 
  19', 
  in 
  15 
  fathoms, 
  

   there 
  are 
  three 
  specimens 
  (No. 
  35531) 
  of 
  considerably 
  larger 
  size 
  which 
  

   agree 
  closely 
  with 
  this 
  species 
  and 
  are 
  i)robably 
  identical. 
  They 
  are 
  

   more 
  extensively 
  encrusted 
  with 
  ferruginous 
  mud 
  and 
  nre 
  somewhat 
  

   higher 
  in 
  proportion 
  to 
  their 
  length; 
  the 
  ventral 
  margin 
  being 
  slightly 
  

   produced 
  in 
  tlie 
  middle, 
  but 
  they 
  have 
  the 
  same 
  posterior 
  angulation 
  

   and 
  the 
  same 
  evenly 
  produced 
  anterior 
  end. 
  The 
  beaks 
  are 
  larger, 
  

   rounded, 
  and 
  reUitively 
  more 
  prominent 
  above 
  the 
  margin. 
  The 
  liinge- 
  

   margin 
  is 
  very 
  tliiu 
  and 
  delicate, 
  but 
  does 
  not 
  differ 
  essentially 
  in 
  other 
  

   respects 
  from 
  the 
  smaller 
  specimens. 
  

  

  Length, 
  2.() 
  mm.; 
  height, 
  2.2 
  mm. 
  

  

  AXINOPSIS 
  ORBICULATA 
  G. 
  O. 
  Sars, 
  variety 
  INEQUALIS, 
  new. 
  

   (riate 
  XCII, 
  lig-.s. 
  5, 
  6.) 
  

  

  Axinopnis 
  orhiciilata 
  G. 
  O. 
  Sar.s, 
  Mollnsca 
  Reg. 
  Arctica^- 
  Norvegia\ 
  p. 
  63, 
  pi. 
  19, 
  

   ligs. 
  Wa-d, 
  1878. 
  — 
  Vekrill, 
  Trans. 
  Couu. 
  Acad., 
  V, 
  p. 
  569, 
  1882.— 
  Bush, 
  

   Proc. 
  U. 
  S. 
  Nat. 
  Mus., 
  VI, 
  p. 
  243, 
  pi. 
  ix, 
  lig. 
  1, 
  1883. 
  

  

  The 
  numerous 
  specimens 
  of 
  this 
  species 
  show 
  considerable 
  variation 
  

   in 
  form 
  and 
  character 
  of 
  the 
  hinge. 
  Many 
  specimens 
  show 
  the 
  cardi- 
  

   nal 
  tooth 
  and 
  pit 
  as 
  described 
  and 
  figured 
  by 
  G. 
  O. 
  Sars; 
  others 
  have 
  

   the 
  hinge-margin 
  nearly 
  smooth 
  or 
  witli 
  mere 
  rudiments 
  of 
  a 
  tooth 
  and 
  

   pit. 
  Our 
  specimens 
  moreover 
  show 
  a 
  thin, 
  continuous 
  external 
  liga- 
  

   ment, 
  which 
  should 
  be 
  lacking 
  according 
  to 
  Sars' 
  description, 
  but 
  he 
  may 
  

   have 
  overlooked 
  it. 
  In 
  form 
  many 
  of 
  our 
  specimens 
  are 
  evenly 
  rounded, 
  

   as 
  ligured 
  by 
  Sars, 
  but 
  others 
  have 
  the 
  antero-dorsal 
  margin 
  more 
  con- 
  

   cave 
  and 
  the 
  anterior 
  end 
  somewhat 
  produced, 
  while 
  the 
  postero-dorsal 
  

   margin 
  is 
  somewhat 
  straighter 
  than 
  usual. 
  

  

  Specimens 
  from 
  the 
  Bay 
  of 
  Fundy 
  have 
  a 
  somewhat 
  oblong 
  form, 
  

   with 
  the 
  ventral 
  margin 
  more 
  nearly 
  straight 
  or 
  but 
  slightly 
  convex, 
  

   and 
  with 
  the 
  anterior 
  end 
  distinctly 
  produced. 
  This 
  form 
  seems 
  suffi 
  

   ciently 
  distinct 
  to 
  receive 
  a 
  varietal 
  name, 
  and 
  we 
  therefore 
  i)ropose 
  to 
  

   call 
  it 
  variety 
  inequalis. 
  

  

  